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  1,1,1,3,3,3-hexafluoropropane purification with photochlorination equipmentUSPTO Application #: 20070102281Title: 1,1,1,3,3,3-hexafluoropropane purification with photochlorination equipment Abstract: c) reacting, in the gaseous state and in the presence of UV light from the photochlorinator, the mixture with Cl2 with the distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated compounds to saturate unsaturated fluorocarbons into a reacted mixture, and d) separating a purified 1,1,1,3,3,3-hexafluoropropane product containing less than 1000 ppm, most preferably less than 100 ppm unsaturated fluorocarbons. b) introducing into the reaction vessel a gaseous mixture of Cl2 and a distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds; A continuous, vapor phase method for purifying a crude mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds, the process comprising: a) providing a photochlorinator vessel comprising: 1) a UV lamp unit comprising a UV lamp located in a transparent inner well, the transparent inner well being located within a transparent outer well, the outer well being provided with material for cooling walls of the inner and outer wells; the inner well and the outer well defining separate chambers isolated from each other; and 2) a reaction vessel into which the UV lamp unit has been inserted; (end of abstract) Agent: Honeywell International Inc. Patent Services Group Ab2 - Morristown, NJ, US Inventors: Yuon Chiu, Daniel C. Merkel, Hsuehsung Tung USPTO Applicaton #: 20070102281 - Class: 204157940 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Non-distilling Bottoms Treatment, Processes Of Treating Materials By Wave Energy, Process Or Preparing Desired Organic Product Containing At Least One Atom Other Than Carbon And Hydrogen, Halogen Product Produced The Patent Description & Claims data below is from USPTO Patent Application 20070102281. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates to a continuous, vapor phase process for purifying 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) to a level of <1000 ppm, preferably <500 ppm, and more preferably <100 ppm, total unsaturates using a UV photochlorinator. BACKGROUND OF THE INVENTION [0002] Due to their stability, relatively low toxicity, compatibility with numerous substances, and low vaporization points, short chain fluorocarbons have been found to have utility or potential utility in industry for many purposes. Such short chain fluorocarbons (about 1 to about 5 carbon atoms) have, for example, been used as propellants, refrigerants, and solvents. [0003] It has been asserted that certain fluorocarbons, especially chlorofluorocarbons, unfortunately may be hazardous to the environment, especially to the ozone layer. Further, impurities in certain fluorocarbons have been found to be troublesome. Unsaturated fluorocarbons are especially undesirable since many of them are toxic and are also often unstable. Such unstable unsaturated fluorocarbons can decompose into even more undesirable products which can be corrosive. It is therefore especially important for certain applications that fluorocarbons be essentially free (e.g. less than 100 ppm) of unsaturated species. There has therefore been a concerted effort to develop new and purer fluorocarbons which are viewed as being more environmentally friendly. [0004] With respect to some fluorocarbons, it has been found possible to reduce the quantity of unsaturated species by chlorination, e.g., as described in U.S. Pat. Nos. 5,190,626 and 5,336,377. Unfortunately, the outcome of such a chlorination technique is not predictable from one fluorocarbon to another, especially when hydrogen is present in the fluorocarbon being purified. This is because hydrogen is frequently replaced by chlorine which reduces yield of the desired product and results in yet further impurities. In certain applications, such fluorocarbons must be especially pure, e.g., when they are used in particularly sensitive areas such as for refrigerants in air conditioners in confined areas. [0005] It has been found that, 1,1,1,3,3,3-hexafluoropropane (HFC-236fa), can be used as a replacement for the fluorocarbon CCl.sub.2F.sub.2CClF.sub.2(CFC-114), used as a refrigerant. HFC-236fa has found particular use as a refrigerant in a closed environment. HFC-236fa can be prepared by numerous methods, e.g., as described in U.S. Pats. No. 5,395,997; 5,414,165; and World Patent Application WO96/15085-A1. 1,1,1,3,3,3-hexafluoropropane might be an excellent replacement for CFC-114, except that pure 1,1,1,3,3,3-hexafluoropropane has not been obtainable by known methods of preparation. This due to the fact that most known methods for the preparation of 1,1,1,3,3,3-hexafluoropropane result in residual impurities of other fluorocarbons. Unfortunately, some of the fluorocarbon impurities form low boiling azeotropes with 1,1,1,3,3,3-hexafluoropropane or are close boiling with 1,1,1,3,3,3-hexafluoropropane, which prevents separation by conventional distillation methods ("distillation inseparable mixtures"). Such distillation inseparable mixtures are obtained when an attempt is made to purify 1,1,1,3,3,3-hexafluoropropane by distillation from the reaction mixture in which it is made. This is especially troublesome since some of the impurities which form azeotropes or close boiling mixtures are unsaturated and cannot be tolerated to any significant extent in refrigerants in certain applications. Examples of such undesirable unsaturated fluorocarbon impurities are 1,1,1,3,3-pentafluoro-2-chloropropene obtained by the liquid phase reaction described in U.S. Pat. No. 5,395,997 and C.sub.3HCl.sub.2F.sub.3 obtained by the vapor phase reaction described in U.S. Pat. No. 5,414,165. [0006] It has been proposed in U.S. Pat. Nos. 5,856,595 and 6,274,779 B1 to purify HFC-236fa from distillation inseparable mixtures of 1,1,1,3,3,3-hexafluoropropane with at least one unsaturated fluorocarbon to obtain a 1,1,1,3,3,3-hexafluoropropane product of greater than 99.9 weight percent purity containing less than 100 parts per million of unsaturated fluorocarbons by a batch, liquid phase method that comprises: a) reacting the mixture with chlorine to saturate the unsaturated fluorocarbons in a reacted mixture, b) distilling the reacted mixture to obtain a 1,1,1,3,3,3-hexafluoroporpane, and c) removing residual HCl and chlorine from the 1,1,1,3,3,3-hexafluoropropane at any point in the method subsequent to reacting the mixture with chlorine to saturate the unsaturated fluorocarbon. [0007] In the method of those patents, it is taught that the reaction of the mixture with chlorine is preferably conducted in the presence of ultraviolet light (UV). However, the patents do not disclose any specific UV photochlorination equipment suitable for use in accomplishing the objective of those patents, nor do patents disclose any photochlorination reaction equipment suitable for conducting the purification reaction in a continuous and vapor phase reaction while still being able to obtain a purified HFC-236fa product containing <100 ppm fluorocarbon unsaturates. It is highly desirable that such a continuous process be obtainable that produces HFC-236fa with <1000 ppm, preferably <500 ppm, and more preferably <100 ppm fluorocarbon unsaturates. BRIEF DESCRIPTION OF THE DRAWINGS [0008] FIG. 1 is a schematic flow diagram illustrating the general method of the invention. [0009] FIG. 2 is a is a elevational schematic view of a photochlorination apparatus used in the method of this invention. [0010] FIG. 3 is a view, partially in section, of a UV Unit of the UV photochlorination apparatus of this invention SUMMARY OF THE INVENTION [0011] In accordance with the invention, a continuous, vapor phase method is provided for the purification of 1,1,1,3,3,3-hexafluoropropane from distillation inseparable mixtures of 1,1,1,3,3,3-hexafluoropropane with at least one unsaturated fluorocarbon to obtain a 1,1,1,3,3,3-hexafluoropropane product containing less than 1000 parts per million, preferably less than 500 parts per million, and more preferably less than 100 parts per million of unsaturated fluorocarbons. Such a product is such as generally to be of greater than 99.9 weight percent purity. [0012] The invention comprises a continuous, vapor phase method for purifying a crude mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds, the process comprising: [0013] a) providing a photochlorinator vessel comprising [0014] 1) a UV lamp unit comprising a UV lamp located in a transparent inner well, the transparent inner well being located within a transparent outer well, said outer well being provided with material for cooling walls of the inner and outer wells; the inner well and the outer well defining separate chambers isolated from each other; and [0015] 2) a reaction vessel into which the UV lamp unit has been inserted; [0016] b) introducing into the reaction vessel a gaseous mixture of Cl.sub.2 and a distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds; [0017] c) reacting, in the gaseous state and in the presence of UV light from the photochlorinator, the mixture with Cl.sub.2 with the distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated compounds to saturate unsaturated fluorocarbons into a reacted mixture, and [0018] d) separating a purified 1,1,1,3,3,3-hexafluoroporpane product containing less than 1000 ppm, preferably less than 500 ppm, and more preferably less than 100 ppm unsaturated fluorocarbons. In another embodiment, step d) comprises distilling the reacted mixture to obtain the purified 1,1,1,3,3,3-hexafluoroporpane product. In a still further embodiment of the invention, the continuous vapor phase method comprises the additional step e) of removing residual HCl and chlorine from the 1,1,1,3,3,3-hexafluoropropane at any point in the method subsequent to reacting the mixture with Cl.sub.2 to saturate the unsaturated fluorocarbons. In an even further embodiment of the invention, step e) is performed between steps c) and d) and comprises washing the reacted mixture with an aqueous solution to remove the residual HCl and chlorine and removing the aqueous solution. [0019] The continuous, vapor phase method preferably comprises: [0020] a) providing a photochlorinator vessel comprising: [0021] 1. a UV lamp unit comprising a UV lamp located in a transparent inner well, the transparent inner well being located within a transparent outer well, said outer well being provided with material for cooling the walls of the inner and outer wells; the inner well and the outer well defining separate chambers isolated from each other; and [0022] 2. a reaction vessel into which the UV lamp unit has been inserted; [0023] b) introducing into the reaction vessel a gaseous mixture of Cl.sub.2 and a distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds; [0024] c) reacting, in the presence of UV light from the photochlorinator, the mixture with Cl.sub.2 with the distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated compounds to saturate the unsaturated fluorocarbon(s) into a reacted mixture, [0025] d) washing the reacted mixture with an aqueous solution to remove residual hydrochloric acid and Cl.sub.2, [0026] e) removing the aqueous solution, [0027] f) distilling the reacted mixture to from which the aqueous solution has been removed to obtain a purified 1,1,1,3,3,3-hexafluoropropane containing <1000 ppm, preferably <500 ppm, and more preferably <100 ppm unsaturated fluorocarbons. DETAILED DESCRIPTION OF THE INVENTION [0028] In accordance with the invention a continuous, vapor phase method is provided to purify HFC-236fa from a crude product mixture containing HFC-236fa and other saturated and unsaturated halocarbons including hydrofluorocarbons (HFC's), chlorofluorocarbons (CFC's) and hydrochlorofluorocarbons (HCFC's), any of which may be saturated or ethylenically unsaturated. The crude product can be produced by several different reaction methods as previously described. The invention comprises a continuous, vapor phase method for purifying a crude mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds, the process comprising: [0029] a) providing a photochlorinator vessel comprising [0030] 1) a UV lamp unit comprising a UV lamp located in a transparent inner well, the transparent inner well being located within a transparent outer well, said outer well being provided with material for cooling walls of the inner and outer wells; the inner well and the outer well defining separate chambers isolated from each other; and [0031] 2) a reaction vessel into which the UV lamp unit has been inserted; [0032] b) introducing into the reaction vessel a gaseous mixture of Cl.sub.2 and a distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds; [0033] c) reacting, in the gaseous state and in the presence of UV light from the photochlorinator, the mixture with Cl.sub.2 with the distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated compounds to saturate unsaturated fluorocarbons into a reacted mixture, and [0034] d) separating a purified 1,1,1,3,3,3-hexafluoroporpane product containing less than 1000 ppm, preferably less than 500 ppm, and more preferably less than 100 ppm unsaturated fluorocarbons. In another embodiment, step d) comprises distilling the reacted mixture to obtain the purified 1,1,1,3,3,3-hexafluoroporpane product. In a still further embodiment of the invention, the continuous vapor phase method comprises the additional step e) of removing residual HCl and chlorine from the 1,1,1,3,3,3-hexafluoropropane at any point in the method subsequent to reacting the mixture with Cl.sub.2 to saturate the unsaturated fluorocarbons. In an even further embodiment of the invention, step e) is performed between steps c) and d) and comprises washing the reacted mixture with an aqueous solution to remove the residual HCl and chlorine and removing the aqueous solution. [0035] The continuous, vapor phase method preferably comprises: [0036] a) providing a photochlorinator vessel comprising [0037] 1. a UV lamp unit comprising a UV lamp located in a transparent inner well, the transparent inner well being located within a transparent outer well, said outer well being provided with material for cooling the walls of the inner and outer wells; and [0038] 2. a reaction vessel into which the UV lamp unit has been inserted; [0039] b) introducing into the reaction vessel a gaseous mixture of Cl.sub.2 and a distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated fluorocarbon compounds; [0040] c) reacting, in the presence of UV light from the photochlorinator, the mixture with Cl.sub.2 with the distillation inseparable mixture of 1,1,1,3,3,3-hexafluoropropane and one or more unsaturated compounds to saturate the unsaturated fluorocarbon(s) into a reacted mixture, [0041] d) washing the reacted mixture with an aqueous solution to remove residual hydrochloric acid and Cl.sub.2, [0042] e) removing the aqueous solution, [0043] f) distilling the reacted mixture to from which the aqueous solution has been removed to obtain a purified 1,1,1,3,3,3-hexafluoropropane product containing <1000 ppm, preferably <500 ppm, and more preferably <100 ppm unsaturated fluorocarbons. [0044] Fluorocarbon" as used herein means a carbon chain to which one or more fluorine atoms are attached. The carbon chain may be perfluorinated, i.e., saturated with fluorine, or may only be partially fluorinated. Partially fluorinated carbon chains may be ethylenically unsaturated, i.e. contain alkene structures, and may have attached hydrogen, chlorine, or bromine atoms. The generic term "fluorocarbon" thus includes HFC's, HCFC's and CFC's. Continue reading... Full patent description for 1,1,1,3,3,3-hexafluoropropane purification with photochlorination equipment Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this 1,1,1,3,3,3-hexafluoropropane purification with photochlorination equipment patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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